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A Geometry-Based Soft Shadow Volume Algorithm Using Graphics Hardware. Ulf Assarsson and Tomas Akenine-Möller SIGGRAPH 2003. We present:. A Soft Shadow Volume Algorithm: Area light sources Simple volumetric light sources Textures and short video textures as lights
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A Geometry-Based Soft Shadow Volume AlgorithmUsing Graphics Hardware Ulf Assarsson and Tomas Akenine-Möller SIGGRAPH 2003
We present: A Soft Shadow Volume Algorithm: • Area light sources • Simple volumetric light sources • Textures and short video textures as lights • Real-time performance with programmable graphics hardware • Approximate soft shadows • Trade speed vs accuracy
A short recap… HARD SOFT Area/volumetric lights give soft shadows • Real lights have area or volume • Thus, soft shadows more realistic
Overview Computation of visibility mask: • 1st pass: Render hard shadow • 2nd pass: compensate for overstated umbra
point source area source umbra penumbra umbra Hard vs. soft shadows Two different light source types:
Wedges • Each silhouette edge has a corresponding wedge • Provides a piece of penumbra contribution • Rasterized by pixelshader
Visibility computation • Really want to compute how much we can see of the light source
Precomputed contribution in 4D textures contribution area 32 32
Examples using textured lights Texture of two colors Texture of 16 area lights
Comparisons Reference image Our algorithm
Comparisons Reference image Our algorithm
Comparisons Small light source Large light source
Comparisons 512 point lights Our algorithm